For a complete understanding and better management of human malignancies we need to learn more about the basic control mechanisms in human tumor cells, particularly the regulation of cell growth and gene expression. As most human malignancies are epithelial and the basic derangement in cancer is at the cellular level, a clone of human carcinoma cells in culture (HeLa, in this study) present great advantages for some of these questions. About 11 homodisperse small RNAs have been described in various subcellular fractions of mammalian cells, and it seems most likely that they have different roles in the cell. One of these RNAs (7S) is also found in purified RNA tumor viruses, where its significance is unknown. Several functions have been postulated for these RNAs, including control of gene expression and cell division, and transport and signal transmission between cytoplasm and nucleus. Our overall objective is to learn the roles of these RNAs in the cell, and their regulation. Some of the experiments in this proposal refer to the in vivo subcellular localization of these RNAs, and to their synthesis and metabolism in physiologically synchronized cells, mitotic cells, resting and growing cells, cell-free systems, a temperature-sensitive mutant, and somatic cell hybrids. We have recently described (5, 10, 20) cytoplasmic precursors to two nuclear small RNAs. One of these nuclear RNAs is highly methylated and contains many pseudouridine residues, while both of these nuclear RNAs have methylated blocked 5' termini. Taking advantage of the unique possibilities presented by these precursors, some of the experiments proposed deal with these RNA modifications. The methods used include: gel electrophoresis, RNA fingerprinting, column chromatography, paper electrophoresis, and sucrose gradient centrifugation.